The translocation of whiteheads (Mohoua albicilla) from Kapiti Island into Karori Wildlife Sanctuary

Abstract

Whiteheads (Mohoua albicilla) were translocated in two groups of 30 from Kaptiti Island into the 'mainland island' Karori Wildlife Sanctuary during August 2001 and May 2002. Initial survival in the first two months following translocation was significantly higher for the first translocation (60%) than the second translocation (27%). This survival difference relates to the different times of release, the greater proportion of juveniles in the second translocation, and to the presence of established conspecifics by the time of the second translocation. There was no significant effect of 'soft' or 'hard' release methods on initial survival, apart from delayed release resulting in delayed males dispersing further. There was also no apparent effect of body size or condition on initial survival. Nine territories were formed in the first breeding season, and seventeen territories established inside the sanctuary (plus one outside the main entrance) in the second breeding season. The length of each breeding season was longer in KWS than is known elsewhere for whiteheads. Also productivity was the highest recorded to date, with 3.7 and 3.4 fledgings per female in each season respectively. Overall 33 fledgings were produced in the first season and 61 fledgings in the second season. All first translocation pairs produced double broods each season, but only three second season pairs were double brooded, probably as most were yearlings, although poorer habitat quality may have been a factor. Most pairs were monogamous, but one case of polygyny occurred each season. Incidences of delayed dispersal and helping behaviour also occurred in the second breeding season, with all cooperating individuals being male. Annual adult survival (0.71) was comparable to other whitehead populations, and to other species of the Mohouinae sub-family. Annual juvenile survival (0.55) was higher than known whitehead records and equivalent to the recruitment rate of first season offspring into the breeding population. This resulted in positive population growth for the period following translocation, with recruitment at replacement levels. It was estimated that the Karori Sanctuary area could hold ninety-one breeding territories, giving the area a sustainable population size of 546 - 728 individuals. Whiteheads showed a distinct preference for certain habitat features within KWS, with older forest stands of mahoe dominated mahoe-fivefinger being preferred. All but one territory contained pine trees, which were regularly used as song-posts and foraging sites. Pine forest was also selected if there was a sufficient understory of mahoe and fivefinger. Territories typically contained a gulley with a stream and gentle gradient; these territories would then extend up a ridge along which pine trees were found. Scrub vegetation and areas with a dense sub-canopy were also preferred, presumably for nest sites. Whiteheads avoided entire areas of low scrub alone. Territory size in the founding population was related to resource distribution and an assumption of the ideal despotic distribution model with regard to settlement following sequential reintroduction was supported.